My 20month old has low grade fever (101) swollen painful gums, crying constantly, not eating, blood in mouth after brushing, very bad breath. ?

Get him/her checked!: Sounds like an infection. Given the excellent blood flow in the mouth, infection can spread rapidly. Also, throat/airway complications can quickly result in an unstable kid. Call your pediatrician, and think about visiting the closest children's hospital.

Get this checked: This sounds like stomatitis - a viral infection in the mouth that can be very painful and cause kids to become dehydrated. It is contagious, so i would keep your child home from daycare until it clears. See your doctor to make sure this is the diagnosis, and it's not something more serious. Also, your doc can suggest some medicines that can help the symptoms.

Thrush?: It sounds like a fungal infection called thrush- a fungal infection in the mouth common to children. Your child needs to be seen by a pedodontist to verify this and to prescribe treatment. If it isn't thrush, the pedodontist will be able to correctly diagnose the problem and treat it!

Baby tooth eruption: Your child is at an age where several classes of baby teeth can be coming into the mouth: commonly called teething, it can cause all of the symptoms you describe, even the small temperature change. It also could be coincident with a viral infection. Look to see if teeth are emerging: bleeding, swelling can be visualized, and very well might be the answer here.

Check ears: Check with doctor to see if he has an ear infection.

Viral: Most likely a viral infection in the mouth and throat.Hydrate but probably needs to be seen to confirm.